Excellent plugin, just the simplicity I spent quite some time looking for in a ramdom image widget!
I also came across the issue where sometimes I’d add an image (uploaded or from the Media Library) and it wouldn’t get uploaded. After a bit of testing, it seems to occur when adding an image and having the LINK URL field set to “none”. If having clicked “file URL” or “attachment post URL” it seems to work fine.
Perhaps this is something that can be changed in a future version, as it causes some confusion – especially since the file/attachment URL field doesn’t have any effect on the output anyway.